Method of and explosive for



Reissued July 16, 1935 UNITED STATES PATENT OFFICE METHOD OF ANDEXPIJOSIVE FOR BLASTING DEEP WELL HOLES John M. Jeffries, Wilmington,Del., assignor to Atlas Powder Company, Wilmington, Del., a corporationoi Delaware No Drawing.

Original No. 1,948,583, dated February 2'7, 1934, Serial No. 579,988,December 9, 1931. Application for reissue March 28, 1935,

Serial N 0. 13,534

18 Claims. (c1. 102-6) 5 upon the explosive used. More particularly itrelates to blasting oil and gas wells surely and efl'ectively and toproviding improved explosive assemblies for the various purposes named.

Well holes as deep as 9000 feet are known and deeper ones are likely inthe future. High temperatures are usually encountered. It is obvious,therefore, that severe pressure and temperature conditions are imposedupon explosives in this field of use.

Ordinarily gelatinous explosives are used and this invention isrestricted to high grade gelatinous explosives in which the content ofnitroglycerine or other liquid explosive is or greater. In this workblasting efiectiveness is dependent upon the detonating wave of thegelatinous explosive propagating throughout the entire charge at themaximum rate of detonation. Instances of poor effectiveness andpartially burning charges have been known with the types of gelatinousexplosives now in use.

It is known in the explosives industry that gelatinous explosives losetheir propagation sensitiveness rapidly when subjected to a vacuum, highpressure, high temperatures or rapid temperature changes. Even too muchpressure in the normal packing operation at the factory can result in aproduct of lowered sensitivity to propagation. Obviously, in a longvertical charge even the weight of the gelatinous explosive upon itselfcan result in a similar condition.

Each of the several conditions mentioned above, to which gelatinousexplosives are subjected is thought to exert its effect through theremoval of air from the'explosive. For instance, if a gelatinousexplosive having high propagation sensitiveness is submitted to any ofthe conditions mentioned it will be found to have increased in densityand to have become less sensitive to propagation. A gelatinous explosiveis conceived to have air stirred into it during manufacture and this airexists in the finished product in the form of minute bubbles. Theplastic walls of these bubbles collapse under the influence of thesevere conditions cited above and air is forced from the explosive.

From the very nature of gelatinous explosives and the causes and eiiectscited, it seemed that the gelatinous explosive itself could not bemodified to obviate this dilficulty. Accordingly, my object, which is toprovide more positive, continuous, brisant explosive action fromgelatinous explosives and to assure a higher order of detonation fromtop to bottom of the column of explosive, must be accomplished in otherways.

I have found that granular, non-gelatinized dynamites, or even partiallygelatinized explosives which might be called semi-gelatins, are notnearly so rapidly decreased in propagation sensitiveness by theconditions previously cited.

I am of the opinion that any explosive has a 1 critical pressure abovewhich its propagation sensitiveness is affected and insuilicientaeration may be a partial cause at least. However, in granular,non-gelatlnized explosives or in semigelatins the walls of the air cellsare solid materials largely and not so easily collapsed as is the casewhen the cell walls consist preponderantly of plastic gelatinizednitrocellulose.

Accordingly, my problem was answered by, and my invention consists in,providing a core of granular, non-gelatinized or semi-gelatinizeddynamite in my gelatin of 50% or more nitroglycerin content or liquidsubstitutes. Ordinarily such explosives would not be satisfactory fordeep well holes because of relatively poor resistance to the penetrationof such liquids as water or oil, because their non-plastic nature mightprevent their shape adapting itself to fill torpedoes or the holesthoroughly, because of lower density and in some cases of greater hazardin handling under severe conditions.

The explosive within the types mentioned which has the greatestpropagation sensitiveness is the so-called straight nitroglycerinedynamite. Accordingly, I prefer to use within my gelatins, a core ofstraight nitroglycerine dynamite. However, other straight dynamites arealmost equally satisfactory. While I have expressed a preferred method,it will be understood that my invention includes a core of anynon-gelatinous or semi-gelatinous explosive in a gelatinous explosive of50% or more nitroglycerine content or equivalent explosive, whether saidequivalent is liquid in itself or liquid because it is soluble innitroglycerine. For instance, trinitrotoluene is a solid at ordinarytemperatures, yet it may be dissolved in nitroglycerine to form a liquidmass.

I am aware that cores of more sensitive explo sive have been proposedfor aiding the explosion or detonation of low explosives such as blackpowder and insensitive high explosives such as chlorate powders. I amalso aware that T. N. T. fuse, the so-called Cordeau, has been used withexplosives generally.

Further, inserts of T. N. T. and widely spaced inserts of straightnitroglycerine dynamite have been suggested for gelatins, but only inthe metal torpedoes and not in the paper wrapped factory packages ofgelatin. It has been my experience that widely spaced inserts are notsuflicient for severe conditions, and consequently my specificationdeals with cores, as distinguished from inserts. I advisedly use theterm core as most correctly expressive because I desire my granular,non-gelatinized or semi-gelatinized dynamite to extend for more than 75%of the length of the gelatin, whereas I would consider inserts to meansome lesser condition.

However, my solution of the problem of successfully shooting deep wellholes with cored high grade nitroglycerine content gelatinousexplosives, which is the object of my invention, has never in myknowledge been proposed or used. It accomplishes a very important andpractical purpose.

My gelatinous explosive may be in any diameter or length, provided thatthe core extends for more than 75% of the length of the gelatin. A corewhich extends throughout the entire length of the explosive ispreferred, but any core which extends for over 75% of the length of thegelatin will produce substantially the full effect desired. While I finda core of approximately V2" in diameter or .196 sq. in. in crosssectional area to be suitable, it is to be understood that the inventionis not limited with respect to the particular cross section orarrangement of the core nor to the cross sectional shape of said core.Any desired cross sectional shape may be employed, such as round,square, triangular or other poly onal shape. Irrespective of the shapeemployed, a cross sectional arrangement of approximately .196 sq.

in. is found to be suitable although not limiting.

I prefer to have the core in the vicinity of the center of thegelatinous explosive because it is there best protected from water oroil and against handling hazards in cases where the core might be moresensitive to mechanical effects than the gelatinous explosive itself. Insuch a central position the core oflers least resistance to theconformation of the gelatinous explosives to the torpedo or well hole.Further, it gives greatest assurance of the core lining up mosteifectively. However, the core may be in any desired position in thegelatinous explosive. For the best practical purposes I could makelimitations as to the length of the core and to the position of thecore, also as to whether it is parallel to or at any angle up to a rightangle to the longitudinal axis of the gelatinous explosive. However, Iknow that my invention has more or less effectiveness under any of theconditions and full protection of my invention demands coverage of allforms.

While I have described gelatinous explosives containing 50% or morenitroglycerine or equivalent, it will be understood that any materialwhich colloids the nitrocellulose or equivalent and thus forms agelatinous explosive is within the scope of my claims.

Since the invention resides in the thought of providing a core of a lessgelatinous nature than the main body of the explosive and one moreresistant to being converted into a mass of high density under pressure,irrespective of the particular chemical composition of either the mainbody of explosive or the core. the invention goes even further than thisin that it embodies the basic thought of providing a core in a chargefor shooting deep wells which will preserve its qualities of aerationunder pressure and/or under temperature changes to better advantage thanthe main body of the explosive whether either of these materials isgelatinous or not, and I wish to make it clear that I claim as myinvention any combination of materials constituting a complete explosivecharge likely to be adversely effected by deep well pressures or otherdeep well conditions and wherein there is provided a separatepropagation core of a nature to be more resistant to being rendered ofhigh density under such deep well conditions, than the main body of thecharge.

I will cite some fleldobservations to indicate the great benefitsresultant from my invention. By the use of this cored gelatinousexplosive the following points of superiority were observed in gas wellblasting as compared to gelatinous explosives previously used in thiswork; That maximum explosive energy was obtained, was evi-. denced bythe unusually large pieces of rock which were thrown forcibly from thewell hole; that the element of brisance, or shattering action, wasgreater was indicated by a spray of fine flour-like dust which wasbrought out of the well hole by the gas for several hours following theshot; that the detonating wave propagated the entire length of thegelatinous explosive with a full rate of detonation was indicated by thesteadily increasing volume of sound of the explosion; that a maximumvolume of gas was generated by the explosive in a minimum amount of timewas indicated by the increased height to which debris was thrown in theair by the explosion: that the shock imparted to the gas bearing stratawas greater was indicated by a perceptibly increased earth tremor fromthe explosion; that the detonation of the entire length of gelatinousexplosive took place in a shorter length of time was indicated by therapidity with which the gas cooled down from the heat of detonationafter the explosion. The volume of natural gas produced from wellsblasted by this cored gelatinous explosive was more than was expectedwhen judgment was based on production obtained by previously usedgelatinous explosives.

The field tests were carried on under the observation of men who havespent their lives in drilling, shooting and operating gas and oil wells,and the foregoing statements of improved results represent the result oftheir observations of thus actual tests.

Having described my invention what I claim is:

1. An explosive of the character described comprising a main body ofgelatinous dynamite, and a. core of less gelatinous and more granulardynae mite therein and extending entirely therethrough, said core havinga propagation sensitiveness materially in excem of that of the main(marge under the conditions oi' use.

2. An explosive of the character described comprising a main body ofgelatinous dynamite, and. a core of less gelatinous and more granulardyna- 12. An article 01' manufacture comprising a unit aeration moreeflectively under pressure than the material of the main charge, saidcore extending substantially throughout the length oi! the body 01 mainhigh explosive material, said core being characterized by its mainsensitizer being a highly sensitive liquid organic nitrate of the ordernitroglycerine.

5. An explosive of the character described comprising a body of mainexplosive of a gelatinous nature and a propagation core of an explosivematerial of a less gelatinous and more granular nature, said coreextending throughout substantially the length of the main body ofexplosive and said core being characterized by having as its mainsensitizer a highly sensitive liquid organic nitrate whereby said coreis rendered of higher propagation sensitiveness than the main explosivewhen used under pressure.

6. An explosive of the character described comprising a main body ofgelatinous dynamite, and a core or less gelatinous and more granulardynamite therein, said core extending for more than 75% of the length ofthe main body of gelatinous dynamite and having a propagationsensitiveness materially in excess of that of the main charge undertheconditions of use.

7, An explosive of the character described containing a body of mainhigh explosive material and a core of explosive propagation materialtherein of a nature to maintain its qualities of aeration moreeffectively under pressure than the material of "the main charge, saidcore extending for more than 75% or the length of the main body of highexplosive material and being characterized by its main sensitizer beinga highly sensitive liquid organic nitrate of the order oinitroglycerine.

8. An explosive of the character described comprising a body of mainexplosive of a gelatinous nature, and a propagation core of an explosivematerial of a less gelatinous and more granular nature, said coreextending for more than 15% of the length of the main body of explosiveand being characterized by having as its main sensitizer a highlysensitive liquid organic nitrate whereby said core is-rendered of higherpropagation sensitiveness than the main explosive when usedunderpressure.

9. An article of manufacture comprising a unit of explosive having amain body of gelatinous dynamite, and a core of less gelatinous'and moregranular dynamite therein and extending substantially therethrough, saidcore having a propagation sensitiveness materially in excess of that 01'the main charge under the conditions of use.

10. An article of manufacture comprising a unit of explosive having, amain body of gelatinous dynamite, and a core of less gelatinous and moregranular dynamite extending for more than 75% of the length of the mainbody of gelatinous dynamite, said core having a propagationsensitiveness materially in excess of that of the main charge under theconditions of use.

11. An article of manufacture comprising a unit of explosive having amain body of gelatinous dynamite, and a core of less gelatinous and moregranular dynamite extending entirely therethrough, said core having apropagation sensitiveness materially in excess of that or the maincharge under the cmditions or use.

of explosive having a main body or high explosive material and a core 0!explosive propagation material therein of a nature to maintain itsqualities of aeration more eflectively under pressure than the materialof the main charge, said core extending for more than 75% of the lengthof the main body of high explosive material and being characterized byits main sensitizer being a highly sensitive liquid organic nitrate ofthe order of nitroglyeerlne.

13. An article of manufacture comprising a unit of explosive having amain body of high explosive material and a core or explosive propagationmaterial therein of a nature to maintain its qualities of aeration moreeilectively under pressure than the material of the main charge, saidcore extending substantially throughout the length of the main body andbeing characterized by its main sensitizer being a highly sensitiveliquid organic nitrate of the order of nitroglycerine.

14. An elongated body of explosive for blasting well holes comprising amain body of gelatinous dynamite having less gelatinous and moregranular dynamite of a higher propagation sensitiveness than the mainbody centrally located therein and extending for more than 75% or thelength of said main body.

15. An explosive assembly for deep well blasting comprising an outerbody of main explosive consisting of a gelatine dynamite and apropagation core housed therein and extending for more than 15% of thelength of the outer body of main explosive and consisting of a dynamitehaving a higher propagation sensitiveness than a similar cross sectionalarea or the main explosive and wherein the proportions are such that themain explosive comprises at least 50% of the entire assembly.

16'. A charge for deep well blasting comprising a main .body of gelatinedynamite having straight nitroglycerine dynamite housed thereinthroughout at least 76% of the length of said main body, said main bodyof gelatine dynamite having no less than 50% nitroglycerine content.

1'1. An explosive of the character described containing a body oi. mainexplosive material and a core of explosive propagation material thereinof a nature to maintain its qualities of aeration more effectively underpressure than the material of the main charge, said core extending formore than 75% of the length of the main body of high explosive materialand being characterized by having as its main sensitizer nitroglycerine.

18. The herein described method of shooting deep wells which consists ofexploding therein a charge consisting of a gelatinous main body ofexplosive, and a core of a less gelatinous and a more granularexplosive, said core extending for more than 75% of the length of themain body of explosive and being characterized by its main sensitizerconsisting of a highly sensitive liquid organic nitrate whereby saidcore is rendered of higher propagation sensitiveness than the mainexplosive under the conditions of pressure existing in deep wells.

JOHN M. JEFFRIES.

